I have been watching some sc2 action on youtube and stuff but I am a complete novice, as the last time I have played StarCraft was on the N64.

My question is I am interested in playing Sc2 for the first time and will be playing campaign to understand the game.

Should I start playing or should I not?

pick protoss

its totally worth it

You should play its a fun game but make sure to pick Protoss otherwise don't bother

stay hydrated

pick whatever race you want. And stick with it. or don't, im not your mom.
alle 3 races are really good, but at the very top level of play (master+) terran has a really tough time vs protoss. That's why people suggest it. The thing about terran is you need to keep an eye on your army, it's very easy to counter infantry army. It may litterly 1 second to lose the game because of banelings and storm (high templar ability).

best of luck mate, and welcome to the most challanging game ever, there are no rewards, only a massive learning curve.

Nope, pick protoss man.

Best way to learn is to play through both campaigns (WoL and HotS) to get a general feel for the game. Note that the campaigns have some modified units; the real game won't play exactly the same way, but it's close enough for you to grasp the big concepts.

Things to focus on while playing the campaign:

*Constant worker production. ALWAYS making workers.
*Keeping your money low. Doesn't matter what you're building, just make sure you're using all your money.
*Not getting supply blocked. Keep an eye on your population and available supply and try to be building supply depots or overlords before you're blocked. That way you can keep up constant worker and unit production.

These seem like 3 really easy things but they're hard, and the fundamental skills one needs to succeed at SC2. Manage your resources well and you'll be better than most players out there.

Good luck and happy hunting.